This invention relates to an apparatus for sealing centrifuge tubes and, more particularly, to an apparatus for sealing centrifuge tubes mounted in rotor cavities.
There is described in the said Romanauskas application a seal for a centrifuge tube that is vertically oriented. Vertically oriented tubes are particularly useful in density gradient separations in which the density gradient is reoriented from vertical to horizontal and back to vertical for fractionation.
Tube caps prior to those devised by Romanauskas typically were comprised of three parts and were not satisfactory, particularly with vertically oriented tubes. The parts were not only difficult to assemble and use but also if one were to obtain the requisite sealing, a vise was required to hold the closure while being tightened.
The seal described by Romanauskas is one in which a tapered plug is introduced into a centrifuge tube disposed in a rotor cavity having a flared mouth. The plug is forced down by a threaded disc which bears axially against the plug so as to wedge the wall of the tube between the plug and the flared mouth of the rotor cavity. Because of the resiliency of the tube, a relatively strong, leak proof seal is provided that is effective even under the large pressure forces which occur during the centrifugation of vertically oriented tubes. While these seals perform quite satisfactorily, as the diameter of the tubes increases, leakage can sometimes occur, particularly with larger diameter tubes, i.e., those exceeding one inch and more. The leakage problem increases as a function of the diameter of the tube, rotor speed and attitude of the tube, i.e., as the tube approaches the vertical or is parallel to the rotational axis, the pressures exerted on the tube cap increase appreciably. The need exists, therefore, for a relatively easy to use, reliable cap or closure for centrifuge tubes, particularly for the large diameter tubes.
It is therefore an object of this invention to provide an improved seal for a centrifuge tube.
A further object of this invention is to provide an improved seal for vertically oriented centrifuge tubes.